Carrierless ultra wideband wireless signals for conveying application data

ABSTRACT

A method for conveying application data via carrierless ultra wideband wireless signals, and signals embodied in a carrierless ultra wideband waveform. Application data is encoded into wavelets that are transmitted as a carrierless ultra wideband waveform. The carrierless ultra wideband waveform is received by an antenna, and the application data is decoded from the wavelets included in the waveform. The waveforms of the signals include wavelets that have a predetermined shape that is used to modulate the data. The signals may convey, for example, Web pages and executable programs between mobile devices. The signals are low power and can penetrate obstructions making them favorable for use with a wireless node of a network.

CROSS-REFERENCE TO RELATED PATENT DOCUMENTS

The present document contains subject matter related to that disclosedin commonly owned, co-pending application Ser. No. 09/209,460, filedDec. 11, 1998, entitled ULTRA WIDE BANDWIDTH SPREAD-SPECTRUMCOMMUNICATIONS SYSTEM; Ser. No. 09/633,815, filed Aug. 7, 2000, entitledELECTRICALLY SMALL PLANAR UWB ANTENNA; application Ser. No. 09/563,292,filed May 3, 2000, entitled PLANAR ULTRA WIDE BAND ANTENNA WITHINTEGRATED ELECTRONICS; Application Ser. No. 60/207,225, filed May 26,2000, entitled ULTRAWIDEBAND COMMUNICATIONS SYSTEM AND METHOD;application Ser. No. 09/685,198, filed Oct. 10, 2000, entitled ANALOGSIGNAL SEPARATOR FOR UWB VERSUS NARROWBAND SIGNALS; Application Ser. No.60/238,466, filed Oct. 10, 2000, entitled ULTRA WIDE BANDWIDTH NOISECANCELLATION MECHANISM AND METHOD; Application Ser. No. 60/217,099,filed Jul. 10, 2000, entitled MULTIMEDIA WIRELESS PERSONAL AREA SYSTEMNETWORK (WPAN) PHYSICAL LAYER SYSTEM AND METHOD; application Ser. No.09/685,203, filed Oct. 10, 2000, entitled SYSTEM AND METHOD FOR BASEBANDREMOVAL OF NARROWBAND INTERFERENCE IN ULTRA WIDEBAND SIGNALS;application Ser. No. 09/685,197, filed Oct. 10, 2000, entitled MODECONTROLLER FOR SIGNAL ACQUISITION AND TRACKING IN AN ULTRA WIDEBANDCOMMUNICATION SYSTEM; application Ser. No. 09/684,400, filed Oct. 10,2000, entitled ULTRA WIDEBAND COMMUNICATION SYSTEM, METHOD, AND DEVICEWITH LOW NOISE PULSE FORMATION; application Ser. No. 09/685,195, filedOct. 10, 2000, entitled ULTRA WIDE BANDWIDTH SYSTEM AND METHOD FOR FASTSYNCHRONIZATION; application Ser. No. 09/684,401, filed Oct. 10, 2000,entitled ULTRA WIDE BANDWIDTH SYSTEM AND METHOD FOR FAST SYNCHRONIZATIONUSING SUB CODE SPINS; application Ser. No. 09/685,196, filed Oct. 10,2000, entitled ULTRA WIDE BANDWIDTH SYSTEM AND METHOD FOR FASTSYNCHRONIZATION USING MULTIPLE DETECTION ARMS; application Ser. No.09/685,199, filed Oct. 10, 2000, entitled A LOW POWER, HIGH RESOLUTIONTIMING GENERATOR FOR ULTRA-WIDE BANDWIDTH COMMUNICATIONS SYSTEMS;application Ser. No. 09/685,202, filed Oct. 10, 2000, entitled METHODAND SYSTEM FOR ENABLING DEVICE FUNCTIONS BASED ON DISTANCE INFORMATION;application Ser. No., 09/685,205, filed Oct. 10, 2000, entitled SYSTEMAND METHOD FOR GENERATING ULTRA WIDEBAND PULSES; application Ser. No.,09/684,782, filed Oct. 10, 2000, entitled ULTRA WIDEBAND COMMUNICATIONSYSTEM, METHOD, AND DEVICE WITH LOW NOISE RECEPTION; and applicationSer. No., 09/685,200, filed Oct. 10, 2000, entitled LEAKAGE NULLINGRECEIVER CORRELATOR STRUCTURE AND METHOD FOR ULTRA WIDE BANDWIDTHCOMMUNICATION SYSTEM, the entire contents of each of which beingincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to methods and signals for ultrawideband communications, and more particularly to methods and signalsfor conveying application data via carrierless ultra wideband wirelesssignals.

2. Discussion of the Background

Digital information typically takes the form of a stream of binarypulses of a square wave, each pulse representing a bit (i.e., 1 or 0) ofdata. To transmit a digital stream of data, it is well known to use thedigital data stream to modulate a carrier waveform and to transmit themodulated carrier waveform rather than the digital waveform. By usingmodulation, a carrier waveform can be used that is most compatible withthe transmission channel. Typically, these waveforms are high-frequencysinusoids for transmitting signals through space.

A discussion of the reasons data signals are modulated onto carriers isincluded in Sklar, B., “Digital Communications: Fundamentals andApplications,” Prentice Hall, 1988, p. 118, the entire contents of whichare incorporated herein by reference. Signals are launched into spacevia antennas. The design of an antenna is dependent on the wavelength,λ, of the signal being transmitted. A practical example illustrates onereason why signals are modulated onto high-frequency carrier waves. Thewavelength, λ, of a signal is equal to c/f, where c is the speed oflight, or 3×108 m/s, and f is the frequency of the frequency of thesignal being transmitted in Hz. It is well known by those of ordinaryskill in the digital communication art that the aperture of an antennashould be at least as large as the wavelength being transmitted (seeSklar, at p. 118). Given this design constraint, it can be shown that asignal with a frequency, f of 3000 Hz has a wavelength, λ, of c/f, or10⁵ m, which is approximately 60 miles. Of course, it is not realisticto build an antenna with a 60 mile aperture. However, if that samesignal is modulated onto a 30 GHz carrier prior to transmitting it, theantenna can have an aperture of less than ½ inch (see Sklar, at p. 118).

Another consideration is the bandwidth required to transmit an idealsquare wave. An unmodulated, unshaped ideal square wave requires aninfinite amount of bandwidth in the frequency domain. For this reason,it is well known to shape the digital pulses using a filter that willround the edges of the square wave, thereby narrowing the bandwidth ofthe transmitted signal. Pulse shaping and modulation are discussed inWebb, W., “The Complete Wireless Communications Professional: A Guidefor Engineers and Managers,” Artech House Publishers, 1999, pp. 55-64,the entire contents of which is incorporated herein by reference.

When digital information is modulated onto a carrier and transmittedthrough space, the power spectral density of that signal tends to beconcentrated about the frequency of the carrier itself. These signalsare normally generated with large antennas and at high power so that thesignal is not interfered with by noise. The frequency spectrum is, ofcourse, regulated in the United States by the Federal CommunicationsCommission (FCC). Regulation of the frequency spectrum ensures thatthere will not be interference within the various allocated frequencyranges. Since all frequency bands contain noise, there is no practicalreason to regulate transmissions that are lower than the noise.

With the popularization of the Internet, laptop personal computers,personal digital assistants (PDAs), and cellular telephones, society hasbecome more and more dependent on the availability of information andthe ability to share information. With the miniaturization of computingpower, many users of information are now demanding mobile access totheir information. Using conventional methods, exchanging, and sharinginformation requires access to network via a telephone connection, orthrough a direct connection to the network itself. The need for anetwork limits access to and sharing of information to those that canaccess the network.

The challenge, then, as presently recognized, is to develop an approachfor transmitting and receiving information using, for example, mobiledevices such as PDAs, cellular telephones, and laptop personalcomputers. It would be advantageous if the approach was wireless,eliminating the need for direct connection between the sharing devices.It would be advantageous if the approach were to employ communicationstechniques that would not fall under the jurisdiction of regulatoryagencies, thereby allowing for global use.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method forcommunicating information using carrierless wireless signals.

The inventors of the present invention have recognized that low powercarrierless transmissions can be effectively used to communicate at highdata rates without interfering with narrowband or spread spectrumsignals, and if the power is kept sufficiently low, the transmissions donot need to be as broadcast devices. Accordingly, another object of thepresent invention is to encode digital data into multi-phase waveletsthat can be transmitted without a carrier at low power and at high datarates over short distances.

In one embodiment, the present invention is implemented as a method forconveying application data with carrierless ultra wideband wirelesssignals. The application data is encoded into wavelets that aretransmitted without modulating them onto a carrier waveform. In anotherembodiment, the present invention is implemented as a computer datasignal that is embodied in a carrierless ultra wideband waveform.

Consistent with the title of this section, the above summary is notintended to be an exhaustive discussion of all the features orembodiments of the present invention. A more complete, although notnecessarily exhaustive, description of the features and embodiments ofthe invention is found in the section entitled “DESCRIPTION OF THEPREFERRED EMBODIMENTS.”

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the present invention, and many of theattendant advantages thereof, will be readily obtained as the samebecomes better understood by reference to the following detaileddescription when considered in connection with the accompanyingdrawings, wherein:

FIG. 1a is a block diagram of an ultra-wide band (UWB) transceiver,according to the present invention;

FIG. 1b is a diagram for illustrating the operation of the transceiverof FIG. 1a, according to the present invention;

FIG. 2 is a block diagram of the transceiver of FIG. 1a, thatmanipulates a shape of UWB pulses, according to the present invention;and

FIG. 3 is a schematic illustration of a general-purposemicroprocessor-based or digital signal processor-based system, which canbe programmed according to the teachings of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1a is a block diagram of an ultra-wide band (UWB) transceiver. InFIG. 1a , the transceiver includes three major components, namely,receiver 11, radio controller and interface 9, and transmitter 13.Alternatively, the system may be implemented as a separate receiver 11and radio controller and interface 9, and a separate transmitter 13 andradio controller and interface 9. The radio controller and interface 9serves as a media access control (MAC) interface between the UWBwireless communication functions implemented by the receiver 11 andtransmitter 13 and applications that use the UWB communications channelfor exchanging data with remote devices.

The receiver 11 includes an antenna 1 that converts a UWBelectromagnetic waveform into an electrical signal (or optical signal)for subsequent processing. The UWB signal is generated with a sequenceof shape-modulated wavelets, where the occurrence times of theshape-modulated wavelets may also be modulated. For analog modulation,at least one of the shape control parameters is modulated with theanalog signal. More typically, the wavelets take on M possible shapes.Digital information is encoded to use one or a combination of the Mwavelet shapes and occurrence times to communicate information.

In one embodiment of the present invention, each wavelet communicatesone bit, for example, using two shapes such as bi-phase. In otherembodiments of the present invention, each wavelet may be configured tocommunicate nn bits, where M≧2^(nn). For example, four shapes may beconfigured to communicate two bits, such as with quadrature phase orfour-level amplitude modulation. In another embodiment of the presentinvention, each wavelet is a “chip” in a code sequence, where thesequence, as a group, communicates one or more bits. The code can beM-ary at the chip level, choosing from M possible shapes for each chip.

At the chip, or wavelet level, embodiments of the present inventionproduce UWB waveforms. The UWB waveforms are modulated by a variety oftechniques including but not limited to: (i) bi-phase modulated signals(+1, −1), (ii) multilevel bi-phase signals (+1, −1, +a1, −a1, +a2, −a2,. . . , +aN, −aN), (iii) quadrature phase signals (+1, −1, +j, −j), (iv)multi-phase signals (1, −1, exp(+jπ/N), exp(−jπ/N), exp(+jπ2/ N),exp(−jπ2/N), . . . , exp(+j(N−1)/N), exp(−jπ(N−1)/N)), (v) multilevelmulti-phase signals (a_(i) exp(j2πβ/N)| a_(i) ε {1, a1, a2, . . . , aK},β ε {0, 1, . . . , N−1}), (vi) frequency modulated pulses, (vii) pulseposition modulation (PPM) signals (possibly same shape pulse transmittedin different candidate time slots), (viii) M-ary modulated waveformsg_(B) _(i) (t) with B_(i) ε {1, . . . , M}, and (ix) any combination ofthe above waveforms, such as multi-phase channel symbols transmittedaccording to a chirping signaling scheme. The present invention,however, is applicable to variations of the above modulation schemes andother modulation schemes (e.g., as described in Lathi, “Modern Digitaland Analog Communications Systems,” Holt, Rinehart and Winston, 1998,the entire contents of which is incorporated by reference herein), aswill be appreciated by those skilled in the relevant art(s).

Some exemplary waveforms and characteristic equations thereof will nowbe described. The time modulation component, for example, can be definedas follows. Let t_(i) be the time spacing between the (i−1)^(th) pulseand the i^(th) pulse. Accordingly, the total time to the i^(th) pulse is$T_{i} = {\sum\limits_{j = 0}^{i}{t_{j}.}}$

The signal T_(i) could be encoded for data, part of a spreading code oruser code, or some combination thereof. For example, the signal T_(i)could be equally spaced, or part of a spreading code, where T_(i)corresponds to the zero-crossings of a chirp, i.e., the sequence ofT_(i)'s, and where $T_{i} = \sqrt{\frac{i - a}{k}}$

for a predetermined set of a and k. Here, a and k may also be chosenfrom a finite set based on the user code or encoded data.

An embodiment of the present invention can be described using M-arymodulation. Equation 1 below can be used to represent a sequence ofexemplary transmitted or received pulses, where each pulse is a shapemodulated UWB wavelet, g_(B) _(i) (t−T_(i)). $\begin{matrix}{{x(t)} = {\sum\limits_{i = 0}^{\infty}{g_{B_{i}}( {t - T_{i}} )}}} & (1)\end{matrix}$

In the above equation, the subscript i refers to the i^(th) pulse in thesequence of UWB pulses transmitted or received. The wavelet function ghas M possible shapes, and therefore B_(i) represents a mapping from thedata, to one of the M-ary modulation shapes at the i^(th) pulse in thesequence. The wavelet generator hardware (e.g., the UWB waveformgenerator 17) has several control lines (e.g., coming from the radiocontroller and interface 9) that govern the shape of the wavelet.Therefore, B_(i) can be thought of as including a lookup-table for the Mcombinations of control signals that produce the M desired waveletshapes. The encoder 21 combines the data stream and codes to generatethe M-ary states. Demodulation occurs in the waveform correlator 5 andthe radio controller and interface 9 to recover to the original datastream. Time position and wavelet shape are combined into the pulsesequence to convey information, implement user codes, etc.

In the above case, the signal is comprised of wavelets from i=1 toinfinity. As i is incremented, a wavelet is produced. Equation 2 belowcan be used to represent a generic wavelet pulse function, whose shapecan be changed from pulse to pulse to convey information or implementuser codes, etc.

 g _(B) _(i) (t)=Re(B _(i,1))·f _(B) _(i,2) _(,B) _(i,3) _(, . . . ,()t)+Im(B _(i,1))·h _(B) _(i,2) _(,B) _(i,3) _(, . . .)(t)  (2)

In the above equation, function f defines a basic wavelet shape, andfunction h is simply the Hilbert transform of the function f. Theparameter B_(i,1) is a complex number allowing the magnitude and phaseof each wavelet pulse to be adjusted, i.e., B_(i,1)=a_(i)∠θ_(i), wherea_(I) is selected from a finite set of amplitudes and θ_(i) is selectedfrom a finite set of phases. The parameters {B_(i,2), B_(i,3), . . . }represent a generic group of parameters that control the wavelet shape.

An exemplary waveform sequence x(t) can be based on a family of waveletpulse shapes f that are derivatives of a Guassian waveform as defined byEquation 3 below. $\begin{matrix}{{f_{B_{i}}(t)} = {{\Psi ( {B_{i,2},B_{i,3}} )}( {\frac{^{B_{i,3}}}{t^{B_{i,3}}}^{- {\lbrack B_{i,2^{t}}\rbrack}^{2}}} )}} & (3)\end{matrix}$

In the above equation, the function Ψ( ) normalizes the peak absolutevalue of f_(B) _(i) (t) to 1. The parameter B_(i,2) controls the pulseduration and center frequency. The parameter B_(i,3) is the number ofderivatives and controls the bandwidth and center frequency.

Another exemplary waveform sequence x(t) can be based on a family ofwavelet pulse shapes f that are Gaussian weighted sinusoidal functions,as described by Equation 4 below.

f _(B) _(i,2) _(,B) _(i,3) _(,B) _(i,4) =f _(ω) _(i) _(,k) _(i) _(,b)_(i) (t)=e ^(−[b) ^(_(i)) ^(1]) ² sin(ω_(i) t+k _(i) t ²).  (4)

In the above equation, b_(i) controls the pulse duration, ω_(i) controlsthe center frequency, and k_(i) controls a chirp rate. Other exemplaryweighting functions, beside Gaussian, that are also applicable to thepresent invention include, for example, Rectangular, Hanning, Hamming,Blackman-Harris, Nutall, Taylor, Kaiser, Chebychev, etc.

Another exemplary waveform sequence x(t) can be based on a family ofwavelet pulse shapes f that are inverse-exponentially weightedsinusoidal functions, as described by Equation 5 below. $\begin{matrix}{{g_{B_{i}}(t)} = {( {\frac{1}{^{\frac{- {({t - {t1}_{i}})}}{{.3}*{tr}_{i}}} + 1} - \frac{1}{^{\frac{- {({t - {t2}_{i}})}}{{.3}*{tf}_{i}}} + 1}} ) \cdot {\sin ( {\theta_{i} + {\omega_{i}t} + {k_{i}t^{2}}} )}}} & (5)\end{matrix}$

where {Bi,_(i,2),B_(i,3),B_(i,4),B_(i,5),B_(i,6),B_(i,7),B_(i,8)}={t1_(i), t2 _(i),tr_(i),tf_(i),θ_(i),ω_(i),k_(i)}

In the above equation, the leading edge turn on time is controlled byt1, and the turn-on rate is controlled by tr. The trailing edge turn-offtime is controlled by t2, and the turn-off rate is controlled by tf.Assuming the chirp starts at t=0 and T_(D) is the pulse duration, thestarting phase is controlled by θ, the starting frequency is controlledby ω, the chirp rate is controlled by k, and the stopping frequency iscontrolled by ω+kT_(D). An example assignment of parameter values isω=1, tr=tf=0.25, t1=tr/0.51, and t2=T_(D)−tr/9.

A feature of the present invention is that the M-ary parameter set usedto control the wavelet shape is chosen so as to make a UWB signal,wherein the center frequency f_(c) and the bandwidth B of the powerspectrum of g(t) satisfies 2f_(c)>B>0.25f_(c). It should be noted thatconventional equations define in-phase and quadrature signals (e.g.,often referred to as I and Q) as sine and cosine terms. An importantobservation, however, is that this conventional definition is inadequatefor UWB signals. The present invention recognizes that use of suchconventional definition may lead to DC offset problems and inferiorperformance.

Furthermore, such inadequacies get progressively worse as the bandwidthmoves away from 0.25f_(c) and toward 2f_(c). A key attribute of theexemplary wavelets (or e.g., those described in co-pending U.S. patentapplication Ser. No. 09/209,460) is that the parameters are chosen suchthat neither f nor h in Equation 2 above has a DC component, yet f and hexhibit the required wide relative bandwidth for UWB systems.

Similarly, as a result of B>0.25f_(c), it should be noted that thematched filter output of the UWB signal is typically only a few cycles,or even a single cycle. For example, the parameter n in Equation 3 abovemay only take on low values (e.g., such as those described in co-pendingU.S. patent application Ser. No. 09/209,460).

The compressed (i.e., coherent matched filtered) pulse width of a UWBwavelet will now be defined with reference to FIG. 1b. In FIG. 1b, thetime domain version of the wavelet thus represents g(t) and the Fouriertransform (FT) version is represented by G(ω). Accordingly, the matchedfilter is represented as G*(ω), the complex conjugate, so that theoutput of the matched filter is P(ω)=G(ω)·G*(ω). The output of thematched filter in the time domain is seen by performing an inverseFourier transform (IFT) on P(ω) so as to obtain p(t), the compressed ormatched filtered pulse. The width of the compressed pulse p(t) isdefined by T_(c), which is the time between the points on the envelopeof the compressed pulse E(t) that are 6 dB below the peak thereof, asshown in FIG. 1b. The envelope waveform E(t) may be determined byEquation 6 below.

E(t)={square root over ((p(t))²+(p ^(H)(t))²)}  (6)

where p^(H) (t) is the Hilbert transform of p(t).

Accordingly, the above-noted parameterized waveforms are examples of UWBwavelet functions that can be controlled to communicate information witha large parameter space for making codes with good resultingautocorrelation and cross-correlation functions. For digital modulation,each of the parameters is chosen from a predetermined list according toan encoder that receives the digital data to be communicated. For analogmodulation, at least one parameter is changed dynamically according tosome function (e.g., proportionally) of the analog signal that is to becommunicated.

Referring back to FIG. 1a, the electrical signals coupled in through theantenna 1 are passed to a radio front end 3. Depending on the type ofwaveform, the radio front end 3 processes the electric signals so thatthe level of the signal and spectral components of the signal aresuitable for processing in the UWB waveform correlator 5. The UWBwaveform correlator 5 correlates the incoming signal (e.g., as modifiedby any spectral shaping, such as a matched filtering, partially matchedfiltering, simply roll-off, etc., accomplished in front end 3) withdifferent candidate signals generated by the receiver 11, so as todetermine when the receiver 11 is synchronized with the received signaland to determine the data that was transmitted.

The timing generator 7 of the receiver 11 operates under control of theradio controller and interface 9 to provide a clock signal that is usedin the correlation process performed in the UWB waveform correlator 5.Moreover, in the receiver 11, the UWB waveform correlator 5 correlatesin time a particular pulse sequence produced at the receiver 11 with thereceive pulse sequence that was coupled in through antenna 1 andmodified by front end 3. When the two such sequences are aligned withone another, the UWB waveform correlator 5 provides high signal to noiseratio (SNR) data to the radio controller and interface 9 for subsequentprocessing. In some circumstances, the output of the UWB waveformcorrelator 5 is the data itself. In other circumstances, the UWBwaveform correlator 5 simply provides an intermediate correlationresult, which the radio controller and interface 9 uses to determine thedata and determine when the receiver 11 is synchronized with theincoming signal.

In some embodiments of the present invention, when synchronization isnot achieved (e.g., during a signal acquisition mode of operation), theradio controller and interface 9 provides a control signal to thereceiver 11 to acquire synchronization. In this way, a sliding of acorrelation window within the UWB waveform correlator 5 is possible byadjustment of the phase and frequency of the output of the timinggenerator 7 of the receiver 11 via a control signal from the radiocontroller and interface 9. The control signal causes the correlationwindow to slide until lock is achieved. The radio controller andinterface 9 is a processor-based unit that is implemented either withhard wired logic, such as in one or more application specific integratedcircuits (ASICs) or in one or more programmable processors.

Once synchronized, the receiver 11 provides data to an input port (“RXData In”) of the radio controller and interface 9. An external process,via an output port (“RX Data Out”) of the radio controller and interface9, may then use this data. The external process may be any one of anumber of processes performed with data that is either received via thereceiver 11 or is to be transmitted via the transmitter 13 to a remotereceiver.

During a transmit mode of operation, the radio controller and interface9 receives source data at an input port (“TX Data In”) from an externalsource. The radio controller and interface 9 then applies the data to anencoder 21 of the transmitter 13 via an output port (“TX Data Out”). Inaddition, the radio controller and interface 9 provides control signalsto the transmitter 13 for use in identify ing the signaling sequence ofUWB pulses. In some embodiments of the present invention, the receiver11 and the transmitter 13 functions may use joint resources, such as acommon timing generator and/or a common antenna, for example. Theencoder 21 receives user coding information and data from the radiocontroller and interface 9 and preprocesses the data and coding so as toprovide a timing input for the UWB waveform generator 17, which producesUWB pulses encoded in shape and/or time to convey the data to a remotelocation.

The encoder 21 produces the control signals necessary to generate therequired modulation. For example, the encoder 21 may take a serial bitstream and encode it with a forward error correction (FEC) algorithm(e.g., such as a Reed Solomon code, a Golay code, a Hamming code, aConvolutional code, etc.). The encoder 21 may also interleave the datato guard against burst errors. The encoder 21 may also apply a whiteningfunction to prevent long strings of “ones” or “zeros.” The encoder 21may also apply a user specific spectrum spreading function, such asgenerating a predetermined length chipping code that is sent as a groupto represent a bit (e.g., inverted for a “one” bit and non-inverted fora “zero” bit, etc.). The encoder 21 may divide the serial bit streaminto subsets in order to send multiple bits per wavelet or per chippingcode, and generate a plurality of control signals in order to affect anycombination of the modulation schemes as described above (and/or asdescribed in Lathi).

The radio controller and interface 9 may provide some identification,such as user ID, etc., of the source from which the data on the inputport (“TX Data In”) is received. In one embodiment of the presentinvention, this user ID may be inserted in the transmission sequence, asif it were a header of an information packet. In other embodiments ofthe present invention, the user ID itself may be employed to encode thedata, such that a receiver receiving the transmission would need topostulate or have a priori knowledge of the user ID in order to makesense of the data. For example, the ID may be used to apply a differentamplitude signal (e.g., of amplitude “f”) to a fast modulation controlsignal to be discussed with respect to FIG. 2, as a way of impressingthe encoding onto the signal.

The output from the encoder 21 is applied to a UWB waveform generator17. The UWB waveform generator 17 produces a UWB pulse sequence of pulseshapes at pulse times according to the command signals it receives,which may be one of any number of different schemes. The output from theUWB generator 17 is then provided to an antenna 15, which then transmitsthe UWB energy to a receiver.

In one UWB modulation scheme, the data may be encoded by using therelative spacing of transmission pulses (e.g., PPM, chirp, etc.). Inother UWB modulation schemes, the data may be encoded by exploiting theshape of the pulses as described above (and/or as described in Lathi).It should be noted that the present invention is able to combine timemodulation (e.g., such as pulse position modulation, chirp, etc.) withother modulation schemes that manipulate the shape of the pulses.

There are numerous advantages to the above capability, such ascommunicating more than one data bit per symbol transmitted from thetransmitter 13, etc. An often even more important quality, however, isthe application of such technique to implement spread-spectrum,multi-user systems, which require multiple spreading codes (e.g., suchas each with spike autocorrelation functions, and jointly with low peakcross-correlation functions, etc.).

In addition, combining timing, phase, frequency, and amplitudemodulation adds extra degrees of freedom to the spreading codefunctions, allowing greater optimization of the cross-correlation andautocorrelation characteristics. As a result of the improvedautocorrelation and cross-correlation characteristics, the systemaccording to the present invention has improved capability, allowingmany transceiver units to operate in close proximity without sufferingfrom interference from one another.

FIG. 2 is a block diagram of a transceiver embodiment of the presentinvention in which the modulation scheme employed is able to manipulatethe shape and time of the UWB pulses. In FIG. 2, when receiving energythrough the antenna 1, 15 (e.g., corresponding antennas 1 and 15 of FIG.1a) the energy is coupled in to a transmit/receive (T/R) switch 27,which passes the energy to a radio front end 3. The radio front end 3filters, extracts noise, and adjusts the amplitude of the signal beforeproviding the same to a splitter 29. The splitter 29 divides the signalup into one of N different signals and applies the N different signalsto different tracking correlators 31 ₁-31 _(N). Each of the trackingcorrelators 31 ₁-31 _(N) receives a clock input signal from a respectivetiming generator 7 ₁-7 _(N) of a timing generator module 7, 19, as shownin FIG. 2.

The timing generators 7 ₁-7 _(N), for example, receive a phase andfrequency adjustment signal, as shown in FIG. 2, but may also receive afast modulation signal or other control signal(s) as well. The radiocontroller and interface 9 provides the control signals, such as phase,frequency and fast modulation signals, etc., to the timing generatormodule 7, 19, for time synchronization and modulation control. The fastmodulation control signal may be used to implement, for example, chirpwaveforms, PPM waveforms, such as fast time scale PPM waveforms, etc.

The radio controller and interface 9 also provides control signals to,for example, the encoder 21, the waveform generator 17, the filters 23,the amplifier 25, the T/R switch 27, the front end 3, the trackingcorrelators 31 ₁-31 _(N) (corresponding to the UWB waveform correlator 5of FIG. 1a), etc., for controlling, for example, amplifier gains, signalwaveforms, filter passbands and notch functions, alternativedemodulation and detecting processes, user codes, spreading codes, covercodes, etc.

During signal acquisition, the radio controller and interface 9 adjuststhe phase input of, for example, the timing generator 7 ₁, in an attemptfor the tracking correlator 31 ₁ to identify and the match the timing ofthe signal produced at the receiver with the timing of the arrivingsignal. When the received signal and the locally generated signalcoincide in time with one another, the radio controller and interface 9senses the high signal strength or high SNR and begins to track, so thatthe receiver is synchronized with the received signal.

Once synchronized, the receiver will operate in a tracking mode, wherethe timing generator 7 ₁ is adjusted by way of a continuing series ofphase adjustments to counteract any differences in timing of the timinggenerator 7 ₁ and the incoming signal. However, a feature of the presentinvention is that by sensing the mean of the phase adjustments over aknown period of time, the radio controller and interface 9 adjusts thefrequency of the timing generator 7 ₁ so that the mean of the phaseadjustments becomes zero. The frequency is adjusted in this instancebecause it is clear from the pattern of phase adjustments that there isa frequency offset between the timing generator 7 ₁ and the clocking ofthe received signal. Similar operations may be performed on timinggenerators 7 ₂-7 _(N), so that each receiver can recover the signaldelayed by different amounts, such as the delays caused by multipath(i.e., scattering along different paths via reflecting off of localobjects).

A feature of the transceiver in FIG. 2 is that it includes a pluralityof tracking correlators 31 ₁-31 _(N). By providing a plurality oftracking correlators, several advantages are obtained. First, it ispossible to achieve synchronization more quickly (i.e., by operatingparallel sets of correlation arms to find strong SNR points overdifferent code-wheel segments). Second, during a receive mode ofoperation, the multiple arms can resolve and lock onto differentmultipath components of a signal. Through coherent addition, the UWBcommunication system uses the energy from the different multipath signalcomponents to reinforce the received signal, thereby improving signal tonoise ratio. Third, by providing a plurality of tracking correlatorarms, it is also possible to use one arm to continuously scan thechannel for a better signal than is being received on other arms.

In one embodiment of the present invention, if and when the scanning armfinds a multipath term with higher SNR than another arm that is beingused to demodulate data, the role of the arms is switched (i.e., the armwith the higher SNR is used to demodulate data, while the arm with thelower SNR begins searching). In this way, the communications systemdynamically adapts to changing channel conditions.

The radio controller and interface 9 receives the information from thedifferent tracking correlators 31 ₁-31 _(N) and decodes the data. Theradio controller and interface 9 also provides control signals forcontrolling the front end 3, e.g., such as gain, filter selection,filter adaptation, etc., and adjusting the synchronization and trackingoperations by way of the timing generator module 7, 19.

In addition, the radio controller and interface 9 serves as an interfacebetween the communication link feature of the present invention andother higher level applications that will use the wireless UWBcommunication link for performing other functions. Some of thesefunctions would include, for example, performing range-findingoperations, wireless telephony, file sharing, personal digital assistant(PDA) functions, embedded control functions, location-findingoperations, etc.

On the transmit portion of the transceiver shown in FIG. 2, a timinggenerator 7 ₀ also receives phase, frequency and/or fast modulationadjustment signals for use in encoding a UWB waveform from the radiocontroller and interface 9. Data and user codes (via a control signal)are provided to the encoder 21, which in the case of an embodiment ofthe present invention utilizing time-modulation, passes command signals(e.g., Δt) to the timing generator 7 ₀ for providing the time at whichto send a pulse. In this way, encoding of the data into the transmittedwaveform may be performed.

When the shape of the different pulses are modulated according to thedata and/or codes, the encoder 21 produces the command signals as a wayto select different shapes for generating particular waveforms in thewaveform generator 17. For example, the data may be grouped in multipledata bits per channel symbol. The waveform generator 17 then producesthe requested waveform at a particular time as indicated by the timinggenerator 7 ₀. The output of the waveform generator is then filtered infilter 23 and amplified in amplifier 25 before being transmitted viaantenna 1, 15 by way of the T/R switch 27.

In another embodiment of the present invention, the transmit power isset low enough that the transmitter and receiver are simply alternatelypowered down without need for the T/R switch 27. Also, in someembodiments of the present invention, neither the filter 23 nor theamplifier 25 is needed, because the desired power level and spectrum isdirectly useable from the waveform generator 17. In addition, thefilters 23 and the amplifier 25 may be included in the waveformgenerator 17 depending on the implementation of the present invention.

A feature of the UWB communications system disclosed, is that thetransmitted waveform x(t) can be made to have a nearly continuous powerflow, for example, by using a high chipping rate, where the waveletsg(t) are placed nearly back-to-back. This configuration allows thesystem to operate at low peak voltages, yet produce ample averagetransmit power to operate effectively. As a result, sub-micron geometryCMOS switches, for example, running at one-volt levels, can be used todirectly drive antenna 1, 15, such that the amplifier 25 is notrequired. In this way, the entire radio can be integrated on a singlemonolithic integrated circuit.

Under certain operating conditions, the system can be operated withoutthe filters 23. If, however, the system is to be operated, for example,with another radio system, the filters 23 can be used to provide a notchfunction to limit interference with other radio systems. In this way,the system can operate simultaneously with other radio systems,providing advantages over conventional devices that use avalanching typedevices connected straight to an antenna, such that it is difficult toinclude filters therein.

The UWB transceiver of FIG. 1a or 2 may be used to perform a radiotransport function for interfacing with different applications as partof a stacked protocol architecture. In such a configuration, the UWBtransceiver performs signal creation, transmission and receptionfunctions as a communications service to applications that send data tothe transceiver and receive data from the transceiver much like a wiredI/O port. Moreover, the UWB transceiver may be used to provide awireless communications function to any one of a variety of devices thatmay include interconnection to other devices either by way of wiredtechnology or wireless technology. Thus, the UWB transceiver of FIG. 1aor 2 may be used as part of a local area network (LAN) (connecting fixedstructures or as part of a wireless personal area network (WPAN)connecting mobile devices, for example. In any such implementation, allor a portion of the present invention may be conveniently implemented ina microprocessor system using conventional general purposemicroprocessors programmed according to the teachings of the presentinvention, as will be apparent to those skilled in the microprocessorsystems art. Appropriate software can be readily prepared by programmersof ordinary skill based on the teachings of the present disclosure, aswill be apparent to those skilled in the software art.

FIG. 3 illustrates a processor system 301 upon which an embodimentaccording to the present invention may be implemented. The system 301includes a bus 303 or other communication mechanism for communicatinginformation, and a processor 305 coupled with the bus 303 for processingthe information. The processor system 301 also includes a main memory307, such as a random access memory (RAM) or other dynamic storagedevice (e.g., dynamic RAM (DRAM), static RAM (SRAM), synchronous DRAM(SDRAM), flash RAM), coupled to the bus 303 for storing information andinstructions to be executed by the processor 305. In addition, a mainmemory 307 may be used for storing temporary variables or otherintermediate information during execution of instructions to be executedby the processor 305. The system 301 further includes a read only memory(ROM) 309 or other static storage device (e.g., programmable ROM (PROM),erasable PROM (EPROM), and electrically erasable PROM (EEPROM)) coupledto the bus 303 for storing static information and instructions for theprocessor 305. A storage device 311, such as a magnetic disk or opticaldisc, is provided and coupled to the bus 303 for storing information andinstructions.

The processor system 301 may also include special purpose logic devices(e.g., application specific integrated circuits (ASICs)) or configurablelogic devices (e.g, simple programmable logic devices (SPLDs), complexprogrammable logic devices (CPLDs), or re-programmable fieldprogrammable gate arrays (FPGAs)). Other removable media devices (e.g.,a compact disc, a tape, and a removable magneto-optical media) or fixed,high density media drives, may be added to the system 301 using anappropriate device bus (e.g., a small system interface (SCSI) bus, anenhanced integrated device electronics (IDE) bus, or an ultra-directmemory access (DMA) bus). The system 301 may additionally include acompact disc reader, a compact disc reader-writer unit, or a compactdisc juke box, each of which may be connected to the same device bus oranother device bus.

The processor system 301 may be coupled via the bus 303 to a display313, such as a cathode ray tube (CRT) or liquid crystal display (LCD) orthe like, for displaying information to a system user. The display 313may be controlled by a display or graphics card. The processor system301 includes input devices, such as a keyboard or keypad 315 and acursor control 317, for communicating information and command selectionsto the processor 305. The cursor control 317, for example, is a mouse, atrackball, or cursor direction keys for communicating directioninformation and command selections to the processor 305 and forcontrolling cursor movement on the display 313. In addition, a printermay provide printed listings of the data structures or any other datastored and/or generated by the processor system 301.

The processor system 301 performs a portion or all of the processingsteps of the invention in response to the processor 305 executing one ormore sequences of one or more instructions contained in a memory, suchas the main memory 307. Such instructions may be read into the mainmemory 307 from another computer-readable medium, such as a storagedevice 311. One or more processors in a multi-processing arrangement mayalso be employed to execute the sequences of instructions contained inthe main memory 307. In alternative embodiments, hard-wired circuitrymay be used in place of or in combination with software instructions.Thus, embodiments are not limited to any specific combination ofhardware circuitry and software.

As stated above, the processor system 301 includes at least one computerreadable medium or memory programmed according to the teachings of theinvention and for containing data structures, tables, records, or otherdata described herein. Stored on any one or on a combination of computerreadable media, the present invention includes software for controllingthe system 301, for driving a device or devices for implementing theinvention, and for enabling the system 301 to interact with a humanuser. Such software may include, but is not limited to, device drivers,operating systems, development tools, and applications software. Suchcomputer readable media further includes the computer program product ofthe present invention for performing all or a portion (if processing isdistributed) of the processing performed in implementing the invention.

The computer code devices of the present invention may be anyinterpreted or executable code mechanism, including but not limited toscripts, interpretable programs, dynamic link libraries, Java or otherobject oriented classes, and complete executable programs. Moreover,parts of the processing of the present invention may be distributed forbetter performance, reliability, and/or cost.

The term “computer readable medium” as used herein refers to any mediumthat participates in providing instructions to the processor 305 forexecution. A computer readable medium may take many forms, including butnot limited to, non-volatile media, volatile media, and transmissionmedia. Non-volatile media includes, for example, optical, magneticdisks, and magneto-optical disks, such as the storage device 311.Volatile media includes dynamic memory, such as the main memory 307.Transmission media includes coaxial cables, copper wire and fiberoptics, including the wires that comprise the bus 303. Transmissionmedia may also take the form of acoustic or light waves, such as thosegenerated during radio wave and infrared data communications.

Common forms of computer readable media include, for example, harddisks, floppy disks, tape, magneto-optical disks, PROMs (EPROM, EEPROM,Flash EPROM), DRAM, SRAM, SDRAM, or any other magnetic medium, compactdisks (e.g., CD-ROM), or any other optical medium, punch cards, papertape, or other physical medium with patterns of holes, a carrier wave,carrierless transmissions, or any other medium from which a system canread.

Various forms of computer readable media may be involved in providingone or more sequences of one or more instructions to the processor 305for execution. For example, the instructions may initially be carried ona magnetic disk of a remote computer. The remote computer can load theinstructions for implementing all or a portion of the present inventionremotely into a dynamic memory and send the instructions over atelephone line using a modem. A modem local to system 301 may receivethe data on the telephone line and use an infrared transmitter toconvert the data to an infrared signal. An infrared detector coupled tothe bus 303 can receive the data carried in the infrared signal andplace the data on the bus 303. The bus 303 carries the data to the mainmemory 307, from which the processor 305 retrieves and executes theinstructions. The instructions received by the main memory 307 mayoptionally be stored on a storage device 311 either before or afterexecution by the processor 305.

The processor system 301 also includes a communication interface 319coupled to the bus 303. The communications interface 319 provides atwo-way UWB data communication coupling to a network link 321 that isconnected to a communications network 323 such as a local network (LAN)or personal area network (PAN)323. For example, the communicationinterface 319 may be a network interface card to attach to any packetswitched UWB-enabled personal area network (PAN)323. As another example,the communication interface 319 may be a UWB accessible asymmetricaldigital subscriber line (ADSL) card, an integrated services digitalnetwork (ISDN) card, or a modem to provide a data communicationconnection to a corresponding type of communications line. Thecommunications interface 319 may also include the hardware to provide atwo-way wireless communications coupling other than a UWB coupling, or ahardwired coupling to the network link 321. Thus, the communicationsinterface 319 may incorporate the UWB transceiver of FIG. 2 as part of auniversal interface that includes hardwired and non-UWB wirelesscommunications coupling to the network link 321.

The network link 321 typically provides data communication through oneor more networks to other data devices. For example, the network link321 may provide a connection through a LAN to a host computer 325 or todata equipment operated by a service provider, which provides datacommunication services through an IP (Internet Protocol) network 327.Moreover, the network link 321 may provide a connection through a PAN323to a mobile device 329 such as a personal digital assistant (PDA) laptopcomputer, or cellular telephone. The LAN/PAN communications network 323and IP network 327 both use electrical, electromagnetic or opticalsignals that carry digital data streams. The signals through the variousnetworks and the signals on the network link 321 and through thecommunication interface 319, which carry the digital data to and fromthe system 301, are exemplary forms of carrier waves transporting theinformation. The processor system 301 can transmit notifications andreceive data, including program code, through the network(s), thenetwork link 321 and the communication interface 319.

What is claimed is:
 1. A method for conveying application data withcarrierless ultra wideband wireless signals comprising the steps of:encoding said application data into wavelets having predeterminedshapes, said shapes being at least one of bi-phase modulated, quad-phasemodulated, multilevel bi-phase modulated, and multilevel quad-phasemodulated; transmitting a carrierless ultra wideband waveform via anantenna, said ultra wideband waveform including said wavelets; receivingsaid carrierless ultra wideband waveform with an antenna; and decodingsaid application data from said wavelets included in said carrierlessultra wideband waveform received in said receiving step.
 2. The methodof claim 1, wherein: each shape comprises a pulse suitable for a pulseposition modulation scheme.
 3. A computer data signal embodied in acarrierless ultra wideband waveform including wavelets havingpredetermined shapes, comprising: at least one of: (a) a Web page, (b) acomputer executable program, (c) data, (d) software, (e) digitizedvoice, (f) video, (g) a graphical image, and (h) text, wherein, saidshapes being at least one of bi-phase modulated, quad-phase modulated,multilevel bi-phase modulated, and multilevel quad-phase modulated. 4.The computer data signal of claim 3, wherein: said Web page is definedby a markup language format.
 5. The computer data signal of claim 4,wherein: said markup language is the hand-held device markup language.6. The computer data signal of claim 4, wherein: said markup language isHTML.
 7. The computer data signal of claim 4, wherein: said markuplanguage is XML.
 8. The computer data signal of claim 3, wherein: saidcomputer executable program is a Java program.
 9. The computer datasignal of claim 3, wherein: said executable program is defined by ascripting language.
 10. The computer data signal of claim 9, wherein:said scripting language is Perl.
 11. The computer data signal of claim9, wherein: said scripting language is JavaScript.
 12. The computer datasignal of claim 3, wherein: said executable program is an ActiveXcontrol.
 13. A computer data signal embodied in a carrierless ultrawideband waveform including wavelets having predetermined shapes,comprising: information being exchanged from one device to anotherdevice, wherein the predetermined shapes are at least one of bi-phasemodulated, quad-phase modulated, multilevel bi-phase modulated, andmultilevel quad-phase modulated.
 14. A computer data signal embodied ina carrierless ultra wideband waveform including wavelets havingpredetermined shapes, comprising: status information sent from ane-appliance, wherein the predetermined shapes are at least one ofbi-phase modulated, quad-phase modulated, multilevel bi-phase modulated,and multilevel quad-phase modulated.
 15. A computer data signal embodiedin a carrierless ultra wideband waveform including wavelets havingpredetermined shapes, comprising: network traffic to or from a wirelessnode of network, wherein the predetermined shapes are at least one ofbi-phase modulated, quad-phase modulated, multilevel bi-phase modulated,and multilevel quad-phase modulated.
 16. The computer data signal ofclaim 15, wherein: said wireless node of a network comprises a wirelessrepeater configured to connect devices transmitting carrierless ultrawideband signals to a network by retransmitting the carrierless ultrawideband signals through a carrier-based communication channel.
 17. Acomputer data signal embodied in a carrierless ultra wideband waveformincluding wavelets having predetermined shapes, comprising: informationfor communicating in a hospital environment without interfering withmedical equipment, wherein the predetermined shapes are at least one ofbi-phase modulated, quad-phase modulated, multilevel bi-phase modulated,and multilevel quad-phase modulated.
 18. A computer data signal embodiedin a carrierless ultra wideband waveform including wavelets havingpredetermined shapes, comprising: information for communicating in anaircraft without interfering with aircraft systems, wherein thepredetermined shapes are at least one of bi-phase modulated, quad-phasemodulated, multilevel bi-phase modulated, and multilevel quad-phasemodulated.
 19. A computer data signal embodied in a carrierless ultrawideband waveform including wavelets having predetermined shapes,comprising: information broadcasting location specific information froma beacon, wherein the predetermined shapes are at least one of bi-phasemodulated, quad-phase modulated, multilevel bi-phase modulated, andmultilevel quad-phase modulated.
 20. A computer data signal embodied ina carrierless ultra wideband waveform including wavelets havingpredetermined shapes, comprising: digitized voice information receivedby a monitoring device, wherein the predetermined shapes are at leastone of bi-phase modulated, quad-phase modulated, multilevel bi-phasemodulated, and multilevel quad-phase modulated.